1. Field of the Invention
The present invention relates to a television receiver connected to a multidirectional antenna, and a television receiving method.
2. Description of the Related Art
As an antenna to be connected to a television receiver, a multidirectional antenna capable of electrically switching the directivity of a radio wave received by being controlled in accordance with a predetermined standard is well-known (such an antenna is commonly called a “smart antenna”). With such a multidirectional antenna used, there is executed a process in which, in the event of, for example, initialization or initial setup, while the directivity directions of the multidirectional antenna are sequentially switched, all azimuthal directions are searched. As a consequence, an optimum receive direction is set into the multidirectional antenna, and the optimum receive direction corresponding to the channel is stored into a channel table. As such, in the event of channel selection, an optimum receive direction corresponding to a selected channel is acquired from a channel table.
Further, a receiver including multiple antennas also is well-known. For example, Japanese Unexamined Patent Application Publication No. 2006-157340 (“Patent Publication 1,” herebelow) discloses a television broadcast receiver that includes two antennas, in which an optimum antenna is selected. Further, Japanese Unexamined Patent Application Publication No. 2001-332991 (“Patent Publication 2,” herebelow) discloses a milli-wave band transmitter that includes multiple antennas, in which the receive direction of a receive antenna is controlled corresponding to the receive state. Further, Japanese Unexamined Patent Application Publication No. 2007-155381 (“Patent Publication 3,” herebelow) discloses a radar device the changes the receive direction in units of each column of an antenna element.
The optimum receive direction of the multidirectional antenna can change with, for example, weather. Especially, in the case of a channel having a low reception sensitivity, the optimum receive direction of the multidirectional antenna corresponding to the channel does not always remain unchanged. More specifically, in the case of old data stored in the channel table, there is a probability that the data does not match an optimum receive direction of an actual (present) multidirectional antenna. Hence, among other requirement, there arise a requirement that latest optimum receive directions of the multidirectional antenna is always set.
To satisfy such a requirement, various approaches can be considered. For example, one approach may be such that, in the event of channel selection, it is determined whether a good or desired signal can be acquired even in the optimum receive direction of the multidirectional antenna, of which data is stored in the channel table. As a consequence, in the event that the desired signal cannot be acquired, the all azimuthal directions are searched while the directivity direction of the multidirectional antenna is being serially switched, thereby to set the current optical receive direction is set into the multidirectional antenna.
Further, Japanese Unexamined Patent Application Publication No. 2006-42157 (“Patent Publication 4,” herebelow) discloses a broadcast receiver that determines the receive direction of an antenna in each event of channel selection by a user.
According to the approach, however, there is a probability that a period of time is necessary to search for the optimum receive direction, thereby causing a delay in channel selection.
As such, a receiver developed to attempt resolution of the problem is disclosed in Japanese Unexamined Patent Application Publication No. 2006-42162 (“Patent Publication 5,” herebelow). According to the receiver, an antenna switchable among 16 receive directions is used. First, two signal-receivable directions are detected through an omnidirectional searching process. Then, a searching process is executed from among three directions between two of the directions, and an optimum receive direction is determined, thereby making it possible to reduce the period of time necessary for the antenna direction searching process.
Nevertheless, however, while, as compared to the case of the omnidirectional search, the period of time necessary for the direction searching process is reduced, there is no difference from the fact that the searching process is executed to seek for the optimum receive direction. As such, there still remains the probability of causing a delay in the operation of channel selection.
Such a problem can similarly takes place even with a television receiver of the type including at least two systems of tuner units that are respectively connected to multidirectional antennas capable of electrically switching the directivity of a receive radio wave and that select and receive a television broadcast signal corresponding to a channel selected by a user. However, the cases where the multiple systems are used are limited to, for example, a case where two-screen outputting is performed, an other system other than image output systems is used for external outputting, and a case where a competitive-channel broadcast program is recorded, but the systems are not always used. As such, in order to overcome the above-described problem, it is now considered to effectively utilize the tuner unit of the system not in use.